Protective covers are used on rotary printing presses in order to cover large areas of danger zones, particularly where there are rotating machine parts, such as inking, transfer and impression rolls, which can cause injury to the operators. Such protective covers, however, must be disposed on the printing machines so as to be removable or hingeable to enable maintenance and adjustment work to be carried out. Industry and insurance standards therefore require such protective covers and electrical protection for the same, either to stop the machine or allow only certain machine functions once the protective covers have been removed or hinged open. Controlled mechanical interlocking mechanisms are provided to safeguard these switching and movement sequences, and the interlocking elements thereof interlock the protective covers in the open state. A mechanism of this general kind is disclosed in European Pat. No. P-0063 229 wherein the interlocking elements of the interlocking mechanism are in the form of a catch and associated bolts on the protective cover and are disposed on one side of the press.
The primary disadvantage of this known interlocking mechanism is that additional operations are required to control the movement of the interlocking elements, in this case the catch. Ease of use of the press is thus impaired, particularly if the printer is on one side of the press and the catch must be operated from the other side. There is also the risk of the interlocking mechanism being damaged in the event of an attempt to close the protective cover without previously disengaging the interlock, thus impairing the function of the interlocking mechanism.